Generally, smart terminals including a cellular phone, a smart pad, and a tablet PC are equipped with a display comprised of a liquid crystal display (LCD) panel, the display being exposed.
Due to characteristics of the panel or according to use states by a user, the display is liable to become dirty or be smudged by fingerprints, ambient dust (e.g., greasy marks), or undesired shocks.
To protect the display from an external environment and use the display in a pleasant state, users who use smart terminals including cellular phones attach protective films made of various types of transparent synthetic resins to displays of the smart terminals. The protective films have been sold at a high cost as functions thereof are improved but after service (A/S) therefor has been provided free of charge.
However, in this case, since a seller of the protective films cannot verify whether a protective film used by a user is a protective film sold thereby and there are many reproduction films in the case of an expensive film, the seller should record a sales status in detail.
In addition, if a sold protective film has defects, the seller needs to provide A/S free of charge and, if a buyer of a defective protective film requests exchange, the seller should exchange the protective film. Then, the seller checks sales status information listed in a sales process to verify whether the A/S requested protective film or the exchange requested protective film is a protective film sold thereby. However, this process is very inconvenient.